A typical telecommunications cubicle is designed to hold a number of line cards (typically between four and six), each having 48 or 64 ports. The ports may be simple electrical connections but in modern “fiber to the cabinet” installations are the interface between the network-side optical fiber network and the “legacy” electrical connections to individual customer premises, and thus include optical/electrical transducers.
Such cabinets have a mains electrical power supply which powers the equipment within the cabinet. Typically, the power circuitry incorporates a residual current device (RCD—also known as “Ground Fault Circuit Interrupters”) which will disconnect the active equipment from the mains power supply if certain electrical fault conditions are detected, specifically an imbalance between the current in the live and neutral connections to the power supply, indicative of a leakage of current to earth (ground). Such a leakage may also cause external metallic parts of the cabinet housing to become electrically live, such that a potentially fatal electrical shock may be delivered to a person touching it, so it is important that such a leakage is detected and the equipment shut down until the cause is identified and repaired.
The equipment cabinets are typically provided with backup batteries for use when an RCD activates, or the mains power supply is interrupted for some reason external to the equipment cabinet. The batteries are typically operating at a lower voltage than typical the mains electricity supplies so can be safely connected in circuit even if the RCD has been activated because of an earthing fault. It is difficult to monitor the condition of these batteries remotely as they are only connected in circuit in exceptional and unpredictable circumstances. If the condition of the batteries is inadequate then customer service may be lost in the event that mains power is interrupted or the RCD activated.
Health and Safety regulations dictate that the RCD should be physically checked periodically, which can impose a significant operational burden on the owner of the equipment. To reduce this burden, a tester has been developed which, periodically and without requiring the attendance of an operative, automatically tests the RCD, reports the test results to a remote location, and then resets the RCD.